1. Field of the Invention
The present general inventive concept relates to a digital image processing apparatus, and a method and system thereof. More specifically, the present general inventive concept pertains to a digital image processing apparatus, which can calculate spatially missing color data using color information of neighboring pixels with respect to an output image of a charge coupled device (CCD) adopting a color filter array, and a method thereof.
2. Description of the Related Art
In general, a digital image processing device such as a digital still camera or a digital video camera processes digital images using a single image sensor and adopts a mosaic color filter array pattern. Since an image sensor, such as a charge coupled device (CCD), basically measures only the intensity of light, a color filter array is used to present colors, and a single color is allotted to each pixel.
Missing color data needs to be calculated using color information of neighboring pixels with respect to an output image of the CCD using the color filter array. This process is referred to as a color interpolation or a color demosaicing algorithm.
FIG. 1 is a block diagram illustrating an example of the conventional digital image processing device. As shown in FIG. 1, the digital image processing device includes a lens part 10, a CCD 20, a buffer 30, a digital signal processor (DSP) 40, and an output part 50.
The lens part 10 includes a zoom lens for enlarging and reducing magnification of an object, a focus lens for adjusting focus of the object, and an iris for adjusting the intensity of radiation. The CCD 20, which is used as a coupled device, photoelectrically transforms a photographed image into an electrical signal. The buffer 30 stores the photoelectrically-transformed image.
The DSP 40 interpolates color of output data from the RGB mosaic CCD 20, which has one of red (R), green (G), and blue (B) color at each pixel, so that each pixel can have all of the color data of R, G and B. The output part 50 converts the interpolated data of the DSP 40 to a displayable signal and outputs the converted signal.
FIG. 2 is a detailed block diagram of the DSP 40 in FIG. 1. Referring to FIGS. 2 and 4, an adaptive interpolation logic 42 interpolates colors by using green color G which is similar to luminance. For example, in the RGB mosaic CCD 20 having only one of red (R), green (G), and blue (B) color at each pixel as shown in FIG. 3, the G33 is interpolated with respect to the pixel R33 based on the following equation.
                                                                        G                ⁢                                                                  ⁢                33                            =                              [                                                      G                    ⁢                                                                                  ⁢                    32                                    +                                                            (                                                                        R                          ⁢                                                                                                          ⁢                          33                                                -                                                  R                          ⁢                                                                                                          ⁢                          31                                                                    )                                        /                    2                                    +                                                            (                                                                        G                          ⁢                                                                                                          ⁢                          34                                                +                                                                              (                                                                                          R                                ⁢                                                                                                                                  ⁢                                33                                                            -                                                              R                                ⁢                                                                                                                                  ⁢                                35                                                                                      )                                                    /                          2                                                                    ]                                        /                    2                                                                                                                          =                                                                    (                                                                  G                        ⁢                                                                                                  ⁢                        32                                            +                                              G                        ⁢                                                                                                  ⁢                        34                                                              )                                    /                  2                                +                                                      (                                                                                            -                          R                                                ⁢                                                                                                  ⁢                        31                                            +                                              2                        ⁢                                                                                                  *                                                                                                  ⁢                        R                        ⁢                                                                                                  ⁢                        33                                            -                                              R                        ⁢                                                                                                  ⁢                        35                                                              )                                    /                  4                                                                                        [                  Equation          ⁢                                          ⁢          1                ]            
In Equation 1, G33 is calculated by adding a peak component of R to a linear interpolation value of G to thus generate a high-resolution signal and reduce a “zipper” effect. FIG. 4 depicts such a color interpolation. The signal of high resolution is generated and the “zipper” effect is reduced through the color interpolation method. Difference interpolation logics 46a and 46b each interpolates a difference from G output from the adaptive interpolation logic 42 with respect to R and B using the linear interpolation, and interpolates R and B by adding G output from the adaptive interpolation logic 42. That is, when R and B are interpolated, high frequency of G having a high frequency band is added to realize the high resolution. The above conventional digital image processing device is disclosed in US Publication No. 2003/052981, published on Mar. 20, 2003.
When the conventional digital image system interpolates G, the peak component of R or B is used to enhance the resolution. Similarly, in interpolating R and B, the peak component of G is used to enhance the resolution. However, when only the peak component is used without considering influence on a luminance component, the “zipper” effect is not reduced or the resolution is not enhanced efficiently since the reduction of the “zipper” effect or the resolution enhancement is closely associated with the luminance component.